split up NAK PDU API

src/cfdp/pdu/nak.rs

@@ -9,10 +9,182 @@ use super::{
     add_pdu_crc, generic_length_checks_pdu_deserialization, CfdpPdu, FileDirectiveType, PduError,
     PduHeader, WritablePduPacket,
 };
+
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
-/// Special iterator type for the NAK PDU which allows to iterator over both normal and large file
+#[derive(Debug, PartialEq, Eq, Clone)]
+pub enum SegmentRequests<'a> {
+    U32Pairs(&'a [(u32, u32)]),
+    U64Pairs(&'a [(u64, u64)]),
+}
+
+/// NAK PDU abstraction specialized in the creation of NAK PDUs.
+///
+/// It exposes a specialized API which simplifies to generate these NAK PDUs with the
+/// format according to CFDP chapter 5.2.6.
+#[derive(Debug, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct NakPduCreator<'seg_reqs> {
+    pdu_header: PduHeader,
+    start_of_scope: u64,
+    end_of_scope: u64,
+    segment_requests: Option<SegmentRequests<'seg_reqs>>,
+}
+
+impl<'seg_reqs> NakPduCreator<'seg_reqs> {
+    /// This constructor will set the PDU header [LargeFileFlag] field to the correct value if
+    /// segment requests are passed to it. If the segment request field is [None], it will remain
+    /// to whatever was configured for the PDU header.
+    pub fn new(
+        mut pdu_header: PduHeader,
+        start_of_scope: u64,
+        end_of_scope: u64,
+        segment_requests: Option<SegmentRequests<'seg_reqs>>,
+    ) -> Result<NakPduCreator, PduError> {
+        // Force correct direction flag.
+        pdu_header.pdu_conf.direction = Direction::TowardsSender;
+        if let Some(ref seg_reqs) = segment_requests {
+            match seg_reqs {
+                SegmentRequests::U32Pairs(_) => {
+                    if start_of_scope > u32::MAX as u64 || end_of_scope > u32::MAX as u64 {
+                        return Err(PduError::InvalidStartOrEndOfScopeValue);
+                    }
+                    pdu_header.pdu_conf.file_flag = LargeFileFlag::Normal;
+                }
+                SegmentRequests::U64Pairs(_) => {
+                    pdu_header.pdu_conf.file_flag = LargeFileFlag::Large;
+                }
+            }
+        }
+        let mut nak_pdu = Self {
+            pdu_header,
+            start_of_scope,
+            end_of_scope,
+            segment_requests,
+        };
+        nak_pdu.pdu_header.pdu_datafield_len = nak_pdu.calc_pdu_datafield_len() as u16;
+        Ok(nak_pdu)
+    }
+
+    pub fn start_of_scope(&self) -> u64 {
+        self.start_of_scope
+    }
+
+    pub fn end_of_scope(&self) -> u64 {
+        self.end_of_scope
+    }
+
+    pub fn segment_requests(&self) -> Option<&SegmentRequests> {
+        self.segment_requests.as_ref()
+    }
+
+    pub fn num_segment_reqs(&self) -> usize {
+        match &self.segment_requests {
+            Some(seg_reqs) => match seg_reqs {
+                SegmentRequests::U32Pairs(pairs) => pairs.len(),
+                SegmentRequests::U64Pairs(pairs) => pairs.len(),
+            },
+            None => 0,
+        }
+    }
+
+    pub fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn calc_pdu_datafield_len(&self) -> usize {
+        let mut datafield_len = 1;
+        if self.file_flag() == LargeFileFlag::Normal {
+            datafield_len += 8;
+            datafield_len += self.num_segment_reqs() * 8;
+        } else {
+            datafield_len += 16;
+            datafield_len += self.num_segment_reqs() * 16;
+        }
+        if self.crc_flag() == CrcFlag::WithCrc {
+            datafield_len += 2;
+        }
+        datafield_len
+    }
+}
+
+impl CfdpPdu for NakPduCreator<'_> {
+    fn pdu_header(&self) -> &PduHeader {
+        &self.pdu_header
+    }
+
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::NakPdu)
+    }
+}
+
+impl WritablePduPacket for NakPduCreator<'_> {
+    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
+        let expected_len = self.len_written();
+        if buf.len() < expected_len {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: expected_len,
+            }
+            .into());
+        }
+        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
+        buf[current_idx] = FileDirectiveType::NakPdu as u8;
+        current_idx += 1;
+
+        if let Some(ref seg_reqs) = self.segment_requests {
+            match seg_reqs {
+                SegmentRequests::U32Pairs(pairs) => {
+                    // Unwrap is okay here, the API should prevent invalid values which would trigger a
+                    // panic here.
+                    let start_of_scope = u32::try_from(self.start_of_scope).unwrap();
+                    let end_of_scope = u32::try_from(self.end_of_scope).unwrap();
+                    buf[current_idx..current_idx + 4]
+                        .copy_from_slice(&start_of_scope.to_be_bytes());
+                    current_idx += 4;
+                    buf[current_idx..current_idx + 4].copy_from_slice(&end_of_scope.to_be_bytes());
+                    current_idx += 4;
+                    for (next_start_offset, next_end_offset) in *pairs {
+                        buf[current_idx..current_idx + 4]
+                            .copy_from_slice(&next_start_offset.to_be_bytes());
+                        current_idx += 4;
+                        buf[current_idx..current_idx + 4]
+                            .copy_from_slice(&next_end_offset.to_be_bytes());
+                        current_idx += 4;
+                    }
+                }
+                SegmentRequests::U64Pairs(pairs) => {
+                    buf[current_idx..current_idx + 8]
+                        .copy_from_slice(&self.start_of_scope.to_be_bytes());
+                    current_idx += 8;
+                    buf[current_idx..current_idx + 8]
+                        .copy_from_slice(&self.end_of_scope.to_be_bytes());
+                    current_idx += 8;
+                    for (next_start_offset, next_end_offset) in *pairs {
+                        buf[current_idx..current_idx + 8]
+                            .copy_from_slice(&next_start_offset.to_be_bytes());
+                        current_idx += 8;
+                        buf[current_idx..current_idx + 8]
+                            .copy_from_slice(&next_end_offset.to_be_bytes());
+                        current_idx += 8;
+                    }
+                }
+            }
+        }
+
+        if self.crc_flag() == CrcFlag::WithCrc {
+            current_idx = add_pdu_crc(buf, current_idx);
+        }
+        Ok(current_idx)
+    }
+
+    fn len_written(&self) -> usize {
+        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+    }
+}
+
+/// Special iterator type for the NAK PDU which allows to iterate over both normal and large file
 /// segment requests.
 pub struct SegmentRequestIter<'a, T> {
     seq_req_start: &'a [u8],
@@ -61,107 +233,31 @@ where
     }
 }
 
-/// NAK PDU abstraction.
+/// NAK PDU abstraction specialized in the reading NAK PDUs from a raw bytestream.
 ///
-/// For more information, refer to CFDP chapter 5.2.6.
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
-#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct NakPdu<'seg_reqs> {
+/// This is a zero-copy class where the segment requests can be read using a special iterator
+/// API without the need to copy them.
+///
+/// The NAK format is expected to be conforming to CFDP chapter 5.2.6.
+pub struct NakPduReader<'seg_reqs> {
     pdu_header: PduHeader,
     start_of_scope: u64,
     end_of_scope: u64,
     seg_reqs_raw: &'seg_reqs [u8],
 }
 
-impl<'seg_reqs> NakPdu<'seg_reqs> {
-    pub fn new(
-        mut pdu_header: PduHeader,
-        start_of_scope: u64,
-        end_of_scope: u64,
-        seg_reqs_raw: &'seg_reqs [u8],
-    ) -> Result<NakPdu, PduError> {
-        // Force correct direction flag.
-        pdu_header.pdu_conf.direction = Direction::TowardsSender;
-        if pdu_header.common_pdu_conf().file_flag == LargeFileFlag::Large {
-            if seg_reqs_raw.len() % 16 != 0 {
-                return Err(PduError::InvalidSegmentRequestFormat);
-            }
-        } else {
-            if seg_reqs_raw.len() % 8 != 0 {
-                return Err(PduError::InvalidSegmentRequestFormat);
-            }
-            if start_of_scope > u32::MAX as u64 || end_of_scope > u32::MAX as u64 {
-                return Err(PduError::InvalidStartOrEndOfScopeValue);
-            }
-        }
-        let mut nak_pdu = Self {
-            pdu_header,
-            start_of_scope,
-            end_of_scope,
-            seg_reqs_raw,
-        };
-        nak_pdu.pdu_header.pdu_datafield_len = nak_pdu.calc_pdu_datafield_len() as u16;
-        Ok(nak_pdu)
-    }
-
-    pub fn start_of_scope(&self) -> u64 {
-        self.start_of_scope
-    }
-
-    pub fn end_of_scope(&self) -> u64 {
-        self.end_of_scope
-    }
-
-    pub fn get_normal_segment_requests_iterator(&self) -> Option<SegmentRequestIter<'_, u32>> {
-        if self.file_flag() == LargeFileFlag::Large {
-            return None;
-        }
-        Some(SegmentRequestIter {
-            seq_req_start: self.seg_reqs_raw,
-            current_idx: 0,
-            phantom: PhantomData,
-        })
-    }
-
-    pub fn get_large_segment_requests_iterator(&self) -> Option<SegmentRequestIter<'_, u64>> {
-        if self.file_flag() == LargeFileFlag::Normal {
-            return None;
-        }
-        Some(SegmentRequestIter {
-            seq_req_start: self.seg_reqs_raw,
-            current_idx: 0,
-            phantom: PhantomData,
-        })
-    }
-
-    pub fn num_segment_reqs(&self) -> usize {
-        if self.file_flag() == LargeFileFlag::Large {
-            self.seg_reqs_raw.len() / 16
-        } else {
-            self.seg_reqs_raw.len() / 8
-        }
-    }
-
-    pub fn pdu_header(&self) -> &PduHeader {
+impl CfdpPdu for NakPduReader<'_> {
+    fn pdu_header(&self) -> &PduHeader {
         &self.pdu_header
     }
 
-    fn calc_pdu_datafield_len(&self) -> usize {
-        let mut datafield_len = 1;
-        if self.file_flag() == LargeFileFlag::Normal {
-            datafield_len += 8;
-            datafield_len += self.num_segment_reqs() * 8;
-        } else {
-            datafield_len += 16;
-            datafield_len += self.num_segment_reqs() * 16;
+    fn file_directive_type(&self) -> Option<FileDirectiveType> {
+        Some(FileDirectiveType::NakPdu)
     }
-        if self.crc_flag() == CrcFlag::WithCrc {
-            datafield_len += 2;
-        }
-        datafield_len
 }
 
-    pub fn from_bytes(buf: &'seg_reqs [u8]) -> Result<NakPdu, PduError> {
+impl<'seg_reqs> NakPduReader<'seg_reqs> {
+    pub fn from_bytes(buf: &'seg_reqs [u8]) -> Result<NakPduReader, PduError> {
         let (pdu_header, mut current_idx) = PduHeader::from_bytes(buf)?;
         let full_len_without_crc = pdu_header.verify_length_and_checksum(buf)?;
         // Minimum length of 9: 1 byte directive field and start and end of scope for normal file
@@ -205,81 +301,84 @@ impl<'seg_reqs> NakPdu<'seg_reqs> {
                 u64::from_be_bytes(buf[current_idx..current_idx + 4].try_into().unwrap());
             current_idx += 4;
         }
-        Self::new(
+        Ok(Self {
             pdu_header,
             start_of_scope,
             end_of_scope,
-            &buf[current_idx..full_len_without_crc],
-        )
-    }
+            seg_reqs_raw: &buf[current_idx..full_len_without_crc],
+        })
     }
 
-impl CfdpPdu for NakPdu<'_> {
-    fn pdu_header(&self) -> &PduHeader {
-        &self.pdu_header
+    pub fn start_of_scope(&self) -> u64 {
+        self.start_of_scope
     }
 
-    fn file_directive_type(&self) -> Option<FileDirectiveType> {
-        Some(FileDirectiveType::NakPdu)
-    }
+    pub fn end_of_scope(&self) -> u64 {
+        self.end_of_scope
     }
 
-impl WritablePduPacket for NakPdu<'_> {
-    fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, PduError> {
-        let expected_len = self.len_written();
-        if buf.len() < expected_len {
-            return Err(ByteConversionError::ToSliceTooSmall {
-                found: buf.len(),
-                expected: expected_len,
-            }
-            .into());
-        }
-        let mut current_idx = self.pdu_header.write_to_bytes(buf)?;
-        buf[current_idx] = FileDirectiveType::NakPdu as u8;
-        current_idx += 1;
-
+    /// This function returns [None] if this NAK PDUs contains segment requests for a large file.
+    pub fn get_normal_segment_requests_iterator(&self) -> Option<SegmentRequestIter<'_, u32>> {
         if self.file_flag() == LargeFileFlag::Large {
-            buf[current_idx..current_idx + 8].copy_from_slice(&self.start_of_scope.to_be_bytes());
-            current_idx += 8;
-            buf[current_idx..current_idx + 8].copy_from_slice(&self.end_of_scope.to_be_bytes());
-            current_idx += 8;
-            // Unwrap is okay here, we checked the file flag.
-            let segments_iter = self.get_large_segment_requests_iterator().unwrap();
-            for (next_start_offset, next_end_offset) in segments_iter {
-                buf[current_idx..current_idx + 8].copy_from_slice(&next_start_offset.to_be_bytes());
-                current_idx += 8;
-                buf[current_idx..current_idx + 8].copy_from_slice(&next_end_offset.to_be_bytes());
-                current_idx += 8;
-            }
-        } else {
-            // Unwrap is okay here, the API should prevent invalid values which would trigger a
-            // panic here.
-            let start_of_scope = u32::try_from(self.start_of_scope).unwrap();
-            let end_of_scope = u32::try_from(self.end_of_scope).unwrap();
-            buf[current_idx..current_idx + 4].copy_from_slice(&start_of_scope.to_be_bytes());
-            current_idx += 4;
-            buf[current_idx..current_idx + 4].copy_from_slice(&end_of_scope.to_be_bytes());
-            current_idx += 4;
-            // Unwrap is okay here, we checked the file flag.
-            let segments_iter = self.get_normal_segment_requests_iterator().unwrap();
-            for (next_start_offset, next_end_offset) in segments_iter {
-                buf[current_idx..current_idx + 4].copy_from_slice(&next_start_offset.to_be_bytes());
-                current_idx += 4;
-                buf[current_idx..current_idx + 4].copy_from_slice(&next_end_offset.to_be_bytes());
-                current_idx += 4;
+            return None;
         }
+        Some(SegmentRequestIter {
+            seq_req_start: self.seg_reqs_raw,
+            current_idx: 0,
+            phantom: PhantomData,
+        })
     }
 
-        if self.crc_flag() == CrcFlag::WithCrc {
-            current_idx = add_pdu_crc(buf, current_idx);
+    /// This function returns [None] if this NAK PDUs contains segment requests for a normal file.
+    pub fn get_large_segment_requests_iterator(&self) -> Option<SegmentRequestIter<'_, u64>> {
+        if self.file_flag() == LargeFileFlag::Normal {
+            return None;
         }
-        Ok(current_idx)
-    }
-
-    fn len_written(&self) -> usize {
-        self.pdu_header.header_len() + self.calc_pdu_datafield_len()
+        Some(SegmentRequestIter {
+            seq_req_start: self.seg_reqs_raw,
+            current_idx: 0,
+            phantom: PhantomData,
+        })
     }
 }
 
 #[cfg(test)]
-mod tests {}
+mod tests {
+    use crate::cfdp::{
+        pdu::tests::{common_pdu_conf, TEST_DEST_ID, TEST_SEQ_NUM, TEST_SRC_ID},
+        PduType, TransmissionMode,
+    };
+
+    use super::*;
+
+    #[test]
+    fn test_basic_creator() {
+        let pdu_conf = common_pdu_conf(CrcFlag::NoCrc, LargeFileFlag::Normal);
+        let pdu_header = PduHeader::new_no_file_data(pdu_conf, 0);
+        let nak_pdu =
+            NakPduCreator::new(pdu_header, 0, 0, None).expect("creating NAK PDU creator failed");
+        assert_eq!(nak_pdu.start_of_scope(), 0);
+        assert_eq!(nak_pdu.end_of_scope(), 0);
+        assert_eq!(nak_pdu.segment_requests(), None);
+        assert_eq!(nak_pdu.num_segment_reqs(), 0);
+
+        assert_eq!(nak_pdu.crc_flag(), CrcFlag::NoCrc);
+        assert_eq!(nak_pdu.file_flag(), LargeFileFlag::Normal);
+        assert_eq!(nak_pdu.pdu_type(), PduType::FileDirective);
+        assert_eq!(
+            nak_pdu.file_directive_type(),
+            Some(FileDirectiveType::NakPdu),
+        );
+        assert_eq!(nak_pdu.transmission_mode(), TransmissionMode::Acknowledged);
+        assert_eq!(nak_pdu.direction(), Direction::TowardsSender);
+        assert_eq!(nak_pdu.source_id(), TEST_SRC_ID.into());
+        assert_eq!(nak_pdu.dest_id(), TEST_DEST_ID.into());
+        assert_eq!(nak_pdu.transaction_seq_num(), TEST_SEQ_NUM.into());
+    }
+
+    #[test]
+    fn test_serialization_empty() {}
+
+    #[test]
+    fn test_serialization_one_segment() {}
+}